1. Field of Invention
This invention relates to aircraft flight control systems wherein the pilot actuates flexible cables to selectively position a control quadrant and thereby effect the desired flight control and more particularly to such a system which is redundant and which can continue to be operated throughout its full control regime despite the severance of one of the cables.
2. Description of the Prior Art
In this flight control art, centering springs have been used to position the quadrant under control by flexible cables to a preselected setting, should one of the flexible cables be severed. By selective control rigging, such emergency positioning can provide a predetermined amount of anti-torque and directional control to the tail rotor of a helicopter, for example. However, in such a system the pilot has only this minimal control following cable severance which may not be adequate to cover the wide range of anti-torque requirements with varying helicopter gross weight and ambient operating conditions and would be inadequate for primary surfaces required for pitch and roll control.
In addition, duplicate flexible cables systems and rigid push-pull tube-cable systems have been utilized, but these have proven to have high friction and to be unduly heavy and expensive. There are many prior art patents, such as U.S. Pat. No. 2,280,106, which include mechanisms brought into play upon the severance of a flexible cable which serves to prevent a "hard over" of the flight control surface under control, but in all such systems the pilot cannot exercise control following a cable severance.